1. Field of the Invention
The present invention relates to a seat belt device which restrains a body of an occupant sitting on a seat of an automobile or the like to the seat in case of emergency, for example, and more particularly to a seat belt device provided with a webbing which restrains the body of the occupant to a seat and a webbing guide which comes into slide contact with the webbing and guides the webbing.
2. Description of the Prior Art
Conventionally, as a seat belt device for restraining an occupant on a vehicle or the like to a seat, there has been a three-point-system seat belt device which adopts a continuous webbing.
FIG. 14 shows such a seat belt device 210. A webbing 211 of the seat belt device 210 has one end portion thereof wound in a retractor 212 such that the webbing 211 can be pulled out from the retractor 212 and other end portion thereof anchored to an anchor plate 214 pivotally mounted on a lower portion of a center pillar 213 by way of a through anchor 215 which constitutes a webbing guide. The webbing 211 has a through tongue 216 disposed between the anchor plate 214 and the through anchor 215 engaged with a buckle 218 mounted in an erected posture in the vicinity of a seat 217 in a carbody. Due to such a constitution, the webbing 211 can restrain the occupant (not shown in the drawing) to the seat 217.
In addition to the through anchor 215 and the through tongue 216 described above, the seat belt device 210 is provided with a through belt, a webbing guide at an outlet of the retractor and the like not shown in the drawing as webbing guides for guiding the webbing 211. Belt slots in an elongated hole shape are respectively formed in the webbing guides and the belt slots come into slide contact with webbing 211 which passes through the belts slots so as to guide the webbing 211.
To ensure the favorable performance of winding the webbing 211 and the favorable manipulation feeling at the time of drawing the webbing 211, it is necessary to suppress the friction resistance at a slide contact portion between the belt slot and the webbing 211 as small as possible. To that end, the surface treatment has been applied to the slide contact portion such that the shape of the surface of the slide contact portion is made smooth by covering resin thereon or a fluorine-based paint having a favorably small friction resistance is coated on the slide contact portion.
Among the webbing guides, the through anchor 215 can be formed, for example, by an insert molding such that an insert fitting is covered with a covering resin by molding. Since the through anchor 215 has to bear a load at the time of collision of a vehicle, the through anchor 215 is required to ensure a sufficient mechanical strength to prevent the deformation thereof when the load is applied to the through anchor 215.
With respect to the through anchor formed by an insert molding such that an insert fitting is covered with the covering resin by molding, depending on a molding material, there has been a possibility that as the user uses the seat belt device repeatedly, the friction resistance between the through anchor and the webbing is increased and this ill-affects the webbing winding performance.
Accordingly, to solve such a problem, U.S. Pat. No. 4,618,165 specification discloses a webbing guide which is formed by press-forming a metal sheet and exhibits a low friction and has a high mechanical strength and a high durability. However, this webbing guide is manufactured from a metal plate by a press forming and hence, it extremely pushes up the manufacturing cost compared with the above-mentioned current-type webbing guide and it is also difficult to properly maintain a gap through which the webbing passes. The increase of the manufacturing cost of the webbing guide eventually results in the increase of the manufacturing cost of the whole seat belt device.
The present invention has been made in view of the above-mentioned circumstances and it is an object of the present invention to provide a seat belt device which, while having a simple construction with the least increase of the cost, can maintain the favorable webbing winding performance by favorably and continuously guiding the webbing.
The above-mentioned object of the present invention can be obtained by a seat belt device comprising a webbing restraining a body of an occupant to a seat and a webbing guide for guiding the webbing in such a manner that the webbing guide comes into slide contact with the webbing, wherein the webbing guide includes an insert fitting, a covering resin which covers the insert fitting by molding, and a metal member with which the webbing comes into slide contact, and the metal member has a slide surface thereof which is brought into slide contact with the webbing protruded than the covering resin toward a webbing side.
The above-mentioned object of the present invention can be obtained by a seat belt device comprising a webbing restraining a body of an occupant to a seat and a webbing guide for guiding the webbing in such a manner that the webbing guide comes into slide contact with the webbing, wherein the webbing guide includes an insert fitting, a covering resin which covers the insert fitting by molding, and a metal member with which the webbing comes into slide contact, and the metal member has a slide surface thereof which is brought into slide contact with the webbing protruded more than the covering resin toward a webbing side.
In the seat belt device of the present invention, the webbing, which is guided by the webbing guide while coming into contact with the webbing guide, restrains the body of the occupant to the seat. The portion of the webbing guide which comes into slide contact with the webbing is a metal member. Accordingly, the adhesion of dust to the slide surface (that is, the metal member) of the webbing guide with which the webbing comes into slide contact can be suppressed and hence, the deterioration of the slide performance with the webbing which is generated as time lapses can be decreased whereby the favorable slide performance can be maintained.
The metal member may be mounted on a resin body after the resin body is formed by molding or the metal member may be integrally formed at the time of forming the resin body by molding.
A protruding quantity of the metal member is determined such that webbing does not come into contact with the resin body when the webbing slides over the metal member. When the webbing comes into contact with the resin body when the webbing slides over the metal member, the contact portion receives a relatively high friction and hence is worn. Since this wear decreases the winding performance of the seat belt and hence is not favorable, a protruding quantity of the metal plate is determined to a proper value which prevents the webbing from coming into contact with the resin body. This performance can be maintained even when the width of the metal plate becomes not more than the width of the webbing for achieving the reduction of the manufacturing cost and for making the device lightweight.
Further, in the seat belt device having the above mentioned constitution, by protruding the metal member more than the resin body toward a webbing side, the webbing is prevented from coming into contact with the resin body. Further by setting this protruding quantity to a proper value, even when the width of the metal member is not more than the width of the webbing, the widthwise end portions of the webbing do not come into contact with the resin body. This is because the webbing has a certain degree of rigidity against a curving thereof.
To take the above into consideration, with respect to the webbing guide used in the seat belt device having the above mentioned constitution, it is desirable that the width of the metal member is set to 35-55 mm and it is also preferable that a protruding quantity of the metal member is set to 0.05-1 mm. However, the width and the protruding quantity of the above mentioned metal member are not limited to these values.
To suppress the manufacturing cost, it is preferable to reduce the dimension of the metal member as small as possible so long as the dimension is enough for the practical use. According to the present invention, with the use of the metal member having the minimum dimension enough for the practical use, the webbing winding performance under the low friction can be maintained without incurring the large increase of the manufacturing cost. According to the present invention, by making the width of the metal member smaller than the width of the webbing, it becomes possible to further reduce the manufacturing cost.
In another seat belt device according to the present invention, the webbing which is guided by the webbing guide in a slide contact manner restrains the body of the occupant to the seat. The slide contact portion of the webbing guide which comes into contact with the webbing is made of the metal member. Both peripheral end portions of the metal member in the webbing widthwise direction are formed such that they are disposed at positions retracted from the webbing slide contact surface toward a side opposite to the webbing side and hence, the peripheral end portions and the webbing do not come into contact with each other. It is preferable that both ends of the metal member in the webbing widthwise direction are, for example, bent toward the covering resin or have a thickness thereof made thin compared with a surface of the metal member which mainly comes into slide contact with the webbing.
According to the present invention, since both peripheral end portions of the metal member in the webbing widthwise direction are disposed at positions retracted from the slide contact surface of the webbing toward the side opposite to the webbing side, even when the webbing is displaced or shifted in the widthwise direction, a gap is ensured between the metal member and the webbing due to the rigidity of the webbing and actions such as tension and hence, it becomes possible to prevent the webbing from coming into contact with the peripheral portions of the metal member.
Further, aiming at the reduction of the friction resistance of the metal member, it may be possible to apply a plating such as a chrome plating or a non-electrolytic plating. To further reduce the friction resistance, it may be possible to form a minute irregular surface (by a shot blasting, for example) on the surface of the metal member and thereafter to apply a plating treatment to the surface. Due to such provisions, the webbing winding performance is also enhanced. Further when the manufacturing cost is taken into consideration, a stainless steel member may be used as the metal member thus eliminating the plating treatment.
The metal member may be mounted on the covering resin after the covering resin is formed by molding or the metal member may be integrally formed with the covering resin at the time of forming the covering resin by molding.
To suppress the manufacturing cost, it is preferable that the dimension of the metal member is made as small as possible as long as the dimension is enough for the practical use. With the use of the metal member having the minimum dimension necessary for the practical use, the webbing winding performance under the low friction can be maintained without incurring the large increase of the manufacturing cost.